In the processing of gas, oil or kerosene to ethylene, the liquid is fed in to piping which passes through a heated furnace and exits as a gas. The piping in the furnace is tortuously arranged in a vertical plane and supported from the roof of the furnace. One or more temperature sensing devices are used to sense the temperature of the fluids in the pipes for regulation of the temperature and rate of flow. The piping in the furnace can be independently supported with respect to the temperature sensing device. One such device is illustrated in U.S. Pat. No. 3,911,747.
One of the problems involved with temperature sensing devises in a cracking furnace is their longevity with respect to the piping. As a practical matter, if the temperature sensing device has a life expectancy matched with the life expectancy of the pipe, then repairs and costs are reduced or minimized. In U.S. Pat. No. 4,324,945, a one piece temperature sensing assembly is welded to the piping in a furnace. The temperature sensing assembly is constructed of materials and a wall configuration to minimize stress changes due to temperature effects and to support piping in a furnace and to have a comparable longevity to the life span of the piping. This is accomplished by optimizing wall cross-sections for optimum strength and selected welded locations and materials.